JP2020196024A - Spot welding system - Google Patents

Spot welding system Download PDF

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Publication number
JP2020196024A
JP2020196024A JP2019102777A JP2019102777A JP2020196024A JP 2020196024 A JP2020196024 A JP 2020196024A JP 2019102777 A JP2019102777 A JP 2019102777A JP 2019102777 A JP2019102777 A JP 2019102777A JP 2020196024 A JP2020196024 A JP 2020196024A
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Prior art keywords
spot welding
weight
welding gun
unit
pressing force
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JP2019102777A
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JP7201537B2 (en
Inventor
バンバク グエン
Nguyen Vanbac
バンバク グエン
茂夫 吉田
Shigeo Yoshida
茂夫 吉田
康裕 天方
Yasuhiro Amakata
康裕 天方
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Fanuc Corp
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Fanuc Corp
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Priority to JP2019102777A priority Critical patent/JP7201537B2/en
Priority to US16/844,344 priority patent/US11351626B2/en
Priority to DE102020113610.2A priority patent/DE102020113610A1/en
Priority to CN202010448238.6A priority patent/CN112008218B/en
Publication of JP2020196024A publication Critical patent/JP2020196024A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes
    • B23K11/31—Electrode holders and actuating devices therefor
    • B23K11/314—Spot welding guns, e.g. mounted on robots
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • B23K11/252—Monitoring devices using digital means
    • B23K11/255—Monitoring devices using digital means the measured parameter being a force
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes
    • B23K11/31—Electrode holders and actuating devices therefor
    • B23K11/314—Spot welding guns, e.g. mounted on robots
    • B23K11/315—Spot welding guns, e.g. mounted on robots with one electrode moving on a linear path
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/36—Auxiliary equipment

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Robotics (AREA)
  • Resistance Welding (AREA)

Abstract

To provide a spot welding system that corrects applied force that changes in accordance with a pose of a spot welding gun due to own weight.SOLUTION: A spot welding system 1 comprises: a spot welding gun 2 having: a movable portion 8 including a movable electrode 7; and a drive unit 9 that drives the movable portion 8; a control unit 4 that controls the drive unit 9; an applied pressure sensor 5 that measures pressure applied by the movable electrode 7 of the spot welding gun 2; and an own-weight calculation unit 17 that, in two different poses of the spot welding gun 2, making moving directions of the movable electrode 7 different, calculates own weight of the movable portion 8 on the basis of the applied pressure detected by the applied pressure sensor 5. When applied pressure used to calculate the own weight of the movable portion 8 by means of the own-weight calculation unit 17 is measured, the control unit 4 controls a drive unit 9 by superposing a dither signal on a control signal, and after the calculation of the own weight, corrects the control signal on the basis of the calculated own weight.SELECTED DRAWING: Figure 1

Description

本開示は、スポット溶接システムに関するものである。 The present disclosure relates to a spot welding system.

スポット溶接ガンを第１の姿勢から角度θだけ回転させたときに、第１の姿勢において測定される加圧力と角度θの姿勢において測定される加圧力との変化量δを算出し、変化量δと角度θとの相関関係を記憶しておくスポット溶接システムが知られている（例えば、特許文献１参照。）。
スポット溶接ガンの姿勢を変更したときに、その姿勢における角度θに対応して記憶されている変化量δを読み出して加圧力指令を補正することにより、スポット溶接ガンの姿勢に関わらず均一な加圧力でスポット溶接を行うことができる。 When the spot welding gun is rotated by an angle θ from the first posture, the amount of change δ between the pressing force measured in the first posture and the pressing force measured in the posture of the angle θ is calculated, and the amount of change is calculated. A spot welding system that stores the correlation between δ and the angle θ is known (see, for example, Patent Document 1).
When the posture of the spot welding gun is changed, the amount of change δ stored corresponding to the angle θ in that posture is read out and the pressing force command is corrected, so that uniform application is applied regardless of the posture of the spot welding gun. Spot welding can be performed with pressure.

特開２０１６−８７６６３号公報Japanese Unexamined Patent Publication No. 2016-87663

スポット溶接ガンにおいては、実際には機構部に静止摩擦が発生し、静止摩擦力は変動するため、補正に用いる加圧力の変動量δを精度よく算出するには、加圧力を精度よく測定することが望ましい。 In a spot welding gun, static friction is actually generated in the mechanical part and the static friction force fluctuates. Therefore, in order to accurately calculate the fluctuation amount δ of the pressing force used for correction, the pressing force is measured accurately. Is desirable.

本開示の一態様は、可動電極を含む可動部と、該可動部を駆動する駆動部とを有するスポット溶接ガンと、前記駆動部を制御する制御部と、前記スポット溶接ガンの前記可動電極による加圧力を計測する加圧力センサと、前記可動電極の移動方向を異ならせる前記スポット溶接ガンの異なる２つの姿勢において、前記加圧力センサにより検出された前記加圧力に基づいて前記可動部の自重を算出する自重算出部とを備え、前記制御部は、前記自重算出部により前記可動部の前記自重を算出する際に用いる前記加圧力の計測に際し、制御信号にディザ信号を重畳して前記駆動部を制御し、前記自重が算出された後には、算出された前記自重に基づいて前記制御信号を補正するスポット溶接システムである。 One aspect of the present disclosure comprises a spot welding gun having a movable portion including a movable electrode, a driving portion for driving the movable portion, a control unit for controlling the driving portion, and the movable electrode of the spot welding gun. In two different postures of the pressure sensor that measures the pressing force and the spot welding gun that moves the movable electrode in different directions, the weight of the movable portion is measured based on the pressing force detected by the pressing force sensor. The control unit includes a self-weight calculation unit for calculating, and the control unit superimposes a dither signal on the control signal when measuring the pressing force used when the self-weight calculation unit calculates the self-weight of the movable unit. Is a spot welding system that corrects the control signal based on the calculated own weight after the own weight is calculated.

本開示の一実施形態に係るスポット溶接システムを示す全体構成図である。It is an overall block diagram which shows the spot welding system which concerns on one Embodiment of this disclosure. 図１のスポット溶接システムの通常運転モードにおいてスポット溶接ガンの駆動部に供給される加圧指令信号の一例を示す図である。It is a figure which shows an example of the pressurization command signal supplied to the drive part of the spot welding gun in the normal operation mode of the spot welding system of FIG. 図１のスポット溶接システムの自重計測モードにおいてスポット溶接ガンの駆動部に供給される加圧指令信号の一例を示す図である。It is a figure which shows an example of the pressurization command signal supplied to the drive part of the spot welding gun in the self-weight measurement mode of the spot welding system of FIG. 図３の自重計測モードにおけるスポット溶接ガンの第１の姿勢の一例を示す図である。It is a figure which shows an example of the 1st posture of the spot welding gun in the self-weight measurement mode of FIG. 図３の自重計測モードにおけるスポット溶接ガンの第２の姿勢の一例を示す図である。It is a figure which shows an example of the 2nd posture of the spot welding gun in the self-weight measurement mode of FIG.

本開示の一実施形態に係るスポット溶接システム１について、図面を参照して以下に説明する。
本実施形態に係るスポット溶接システム１は、スポット溶接ガン２と、スポット溶接ガン２を取り付けるロボット３と、ロボット３に接続された制御装置（制御部）４と、スポット溶接ガン２による加圧力を計測する加圧力センサ５とを備えている。 The spot welding system 1 according to the embodiment of the present disclosure will be described below with reference to the drawings.
The spot welding system 1 according to the present embodiment applies pressure from the spot welding gun 2, the robot 3 to which the spot welding gun 2 is attached, the control device (control unit) 4 connected to the robot 3, and the spot welding gun 2. It is provided with a pressure sensor 5 for measuring.

スポット溶接ガン２は、例えば、図１に示されるように、固定溶接チップ６と、可動溶接チップ（可動電極）７と、可動溶接チップ７を含む可動部８を１軸方向に駆動する駆動部９とを備え、全体として略Ｃ形状を有している。
スポット溶接ガン２は、サーボガンであり、駆動部９は、サーボモータ１０と、サーボモータ１０の駆動力により回転させられる図示しないボールねじと、ボールねじに噛み合い可動部８に固定された図示しないナットとを備えている。 As shown in FIG. 1, the spot welding gun 2 is, for example, a driving unit that drives a fixed welding tip 6, a movable welding tip (movable electrode) 7, and a movable portion 8 including the movable welding tip 7 in a uniaxial direction. It has a substantially C shape as a whole.
The spot welding gun 2 is a servo gun, and the drive unit 9 includes a servo motor 10, a ball screw (not shown) rotated by the driving force of the servo motor 10, and a nut (not shown) that meshes with the ball screw and is fixed to the movable portion 8. And have.

スポット溶接ガン２は、サーボモータ１０を駆動することによって可動溶接チップ７を移動させて、固定溶接チップ６と可動溶接チップ７との隙間を開閉し、両チップ６，７間に被溶接物を挟んで加圧する。この状態で、両チップ６，７間に電流を流すことによって被溶接物をスポット溶接する。 The spot welding gun 2 moves the movable welding tip 7 by driving the servomotor 10 to open and close the gap between the fixed welding tip 6 and the movable welding tip 7, and inserts an object to be welded between the tips 6 and 7. Pressurize by sandwiching. In this state, the object to be welded is spot welded by passing an electric current between both tips 6 and 7.

ロボット３は、例えば、６軸多関節型ロボットである。ロボット３は、図１に示されるように、床面Ｆに設置されるベース１１と、鉛直な第１軸線Ａ回りにベース１１に対して回転可能な旋回胴１２とを備えている。また、ロボット３は、水平な第２軸線Ｂ回りに旋回胴１２に対して回転可能な第１アーム１３、第１アーム１３の先端に第２軸線Ｂに平行な第３軸線Ｃ回りに回転可能な第２アーム１４および第２アーム１４の先端に支持された３軸の手首ユニット１５を備えている。 The robot 3 is, for example, a 6-axis articulated robot. As shown in FIG. 1, the robot 3 includes a base 11 installed on the floor surface F, and a swivel cylinder 12 that can rotate with respect to the base 11 around the vertical first axis A. Further, the robot 3 can rotate around the horizontal second axis B with respect to the swivel body 12, and at the tip of the first arm 13 around the third axis C parallel to the second axis B. The second arm 14 and the three-axis wrist unit 15 supported by the tips of the second arm 14 are provided.

ロボット３の手首ユニット１５の先端にスポット溶接ガン２を取り付けることにより、ロボット３の作動によってスポット溶接ガン２の位置および姿勢を任意に変更することができる。
制御装置４は、ロボット３を制御するとともに、スポット溶接ガン２のサーボモータ１０を付加軸として制御する制御信号生成部１６を備えている。 By attaching the spot welding gun 2 to the tip of the wrist unit 15 of the robot 3, the position and posture of the spot welding gun 2 can be arbitrarily changed by the operation of the robot 3.
The control device 4 includes a control signal generation unit 16 that controls the robot 3 and also controls the servomotor 10 of the spot welding gun 2 as an additional axis.

また、制御装置４は、加圧力センサ５からの出力および制御信号生成部１６からの手首ユニット１５の各軸の角度情報に基づいて、スポット溶接ガン２の可動部８の自重を算出する自重算出部１７と、算出された自重を記憶する記憶部１８とを備えている。
加圧力センサ５は、自重計測時に固定溶接チップ６と可動溶接チップ７との間に挟まれる位置に配置され、駆動部９の作動により両チップ６，７から受ける加圧力を計測する。 Further, the control device 4 calculates the own weight of the movable portion 8 of the spot welding gun 2 based on the output from the pressure sensor 5 and the angle information of each axis of the wrist unit 15 from the control signal generation unit 16. It includes a unit 17 and a storage unit 18 that stores the calculated own weight.
The pressing sensor 5 is arranged at a position sandwiched between the fixed welding tip 6 and the movable welding tip 7 at the time of measuring its own weight, and measures the pressing force received from both tips 6 and 7 by the operation of the drive unit 9.

具体的には、制御装置４は、ユーザによって選択可能な自重計測モードと通常動作モードとを切り替えるモード切替部１９を備えている。モードの選択は、例えば、ティーチングペンダントまたは操作盤のスイッチ等の入力部２０を操作することにより行われる。 Specifically, the control device 4 includes a mode switching unit 19 that switches between a self-weight measurement mode and a normal operation mode that can be selected by the user. The mode is selected, for example, by operating an input unit 20 such as a teaching pendant or a switch on an operation panel.

加圧力センサ５が固定溶接チップ６と可動溶接チップ７との間に配置され、入力部２０の操作により自重計測モードが選択されたときには、モード切替部１９は、制御信号生成部１６を自重計測モードに切り替える。自重計測モードでは、制御信号生成部１６は、ロボット３に対し、所定の第１の姿勢にスポット溶接ガン２を配置する制御信号を生成する。制御信号生成部１６によって生成された制御信号は、スポット溶接ガン２の駆動部９を構成しているサーボモータ１０に入力される。 When the pressure sensor 5 is arranged between the fixed welding tip 6 and the movable welding tip 7 and the self-weight measurement mode is selected by the operation of the input unit 20, the mode switching unit 19 measures the self-weight of the control signal generation unit 16. Switch to mode. In the self-weight measurement mode, the control signal generation unit 16 generates a control signal for the robot 3 to arrange the spot welding gun 2 in a predetermined first posture. The control signal generated by the control signal generation unit 16 is input to the servomotor 10 constituting the drive unit 9 of the spot welding gun 2.

この自重計測モードにおける制御信号は、スポット溶接ガン２を所定の姿勢、例えば、可動溶接チップ７が鉛直下方に向かって被溶接物を加圧する姿勢に配置した状態で駆動部９のサーボモータ１０に供給する指令信号（基準加圧力指令：制御信号）に、ディザ信号を重畳している。基準加圧力指令は、例えば、図２に示されるように、目標値Ｘとしてステップ状に変化し、ディザ信号が重畳されていない信号である。 The control signal in this self-weight measurement mode is sent to the servomotor 10 of the drive unit 9 in a state where the spot welding gun 2 is arranged in a predetermined posture, for example, a posture in which the movable welding tip 7 presses the work piece vertically downward. A dither signal is superimposed on the command signal (reference pressurization command: control signal) to be supplied. As shown in FIG. 2, for example, the reference pressurizing command is a signal that changes stepwise as a target value X and does not have a dither signal superimposed.

ディザ信号が重畳されていない場合には、加圧力センサ５により計測される実際の加圧力の応答波形は、静止摩擦の影響により基準加圧力指令の目標値Ｘには到達せず、最終値はＹ＜Ｘとなって偏差が残る。
これに対し、自重計測モードにおける指令信号には、図３に示されるようにディザ信号が重畳されている。ディザ信号は、加圧力センサ５による加圧力の計測値が立ち上がった後、所定時間経過後から基準加圧力指令に重畳される。 When the dither signal is not superimposed, the actual pressure response waveform measured by the pressure sensor 5 does not reach the target value X of the reference pressure command due to the influence of static friction, and the final value is Y <X and the deviation remains.
On the other hand, a dither signal is superimposed on the command signal in the self-weight measurement mode as shown in FIG. The dither signal is superimposed on the reference pressurization command after a predetermined time has elapsed after the measured value of the pressurization by the pressurization sensor 5 has risen.

例えば、ディザ信号の重畳を開始する所定時間としては、ディザ信号を重畳しないで加圧した場合の、図２に示される加圧力値の応答において、静定した加圧力値Ｙの７５％以上８５％未満、好ましくは、８０％となる時点の時間Δｔ１に設定することが好ましい。 For example, the predetermined time for starting the superposition of the dither signal is 75% or more of the statically indeterminate pressure value Y in the response of the pressure value shown in FIG. 2 when the dither signal is pressurized without being superposed. It is preferable to set the time Δt1 at a time point of less than%, preferably 80%.

ディザ信号は周期信号を使用する。例えば、振幅Ａ周波数ｆの正弦波を使用してもよい。振幅Ａについては、可動部８が静止状態から動き出すのに必要な力の大きさで決定することができる。周波数ｆについては、スポット溶接ガン２の固有周波数に近い周波数に設定するとよい。 The dither signal uses a periodic signal. For example, a sine wave having an amplitude A and a frequency f may be used. The amplitude A can be determined by the magnitude of the force required for the movable portion 8 to start moving from the stationary state. The frequency f may be set to a frequency close to the natural frequency of the spot welding gun 2.

また、ディザ信号は、加圧力センサ５により検出される加圧力が静定した時点で、基準加圧力指令への重畳が停止される。すなわち、ディザ信号は、図３に示されるように基準加圧力指令の立ち上がり後Δｔ１からΔｔ２までの期間のみに基準加圧力指令に重畳される。
時間Δｔ１，Δｔ２については、予備的な実験により取得された応答波形に基づいて予め設定しておいてもよい。 Further, when the pressing force detected by the pressing force sensor 5 has settled down, the dither signal is stopped from being superimposed on the reference pressing force command. That is, as shown in FIG. 3, the dither signal is superimposed on the reference pressurization command only during the period from Δt1 to Δt2 after the rise of the reference pressurization command.
The times Δt1 and Δt2 may be set in advance based on the response waveform obtained by the preliminary experiment.

そして、静定した後の加圧力値が加圧力センサ５から自重算出部１７に送られる。これと同時に、手首ユニット１５の各軸の角度も自重算出部１７に送られ、加圧力値と対応付けて一時的に記憶される。 Then, the pressure value after statically indeterminate is sent from the pressure sensor 5 to the own weight calculation unit 17. At the same time, the angle of each axis of the wrist unit 15 is also sent to the self-weight calculation unit 17, and is temporarily stored in association with the pressing force value.

次いで、制御信号生成部１６は、ロボット３に対し、第１の姿勢とは異なる所定の第２の姿勢にスポット溶接ガン２を配置する制御信号を生成する。この場合に生成される制御信号は、第１の姿勢において生成された制御信号と同一の基準加圧力指令に同一のディザ信号を同一期間だけ重畳した信号である。生成された制御信号は、スポット溶接ガン２の駆動部９を構成しているサーボモータ１０へ入力される。 Next, the control signal generation unit 16 generates a control signal for the robot 3 to arrange the spot welding gun 2 in a predetermined second posture different from the first posture. The control signal generated in this case is a signal obtained by superimposing the same dither signal on the same reference pressurizing command as the control signal generated in the first posture for the same period. The generated control signal is input to the servomotor 10 constituting the drive unit 9 of the spot welding gun 2.

自重算出部１７は、スポット溶接ガン２の２つの異なる姿勢において計測された２組の加圧力値と手首ユニット１５の角度とに基づいて、スポット溶接ガン２の可動部８の自重を算出する。
例えば、図４に示されるように、第１の姿勢において、可動部８の移動方向が、鉛直下方に対して鉛直平面内において角度θ１であり、加圧力値がＦ１であるとする。また、図５に示されるように、第２の姿勢において、可動部８の移動方向が、鉛直下方に対して鉛直平面内において角度θ２であり、加圧力値がＦ２であるとする。 The self-weight calculation unit 17 calculates the self-weight of the movable portion 8 of the spot welding gun 2 based on the two sets of pressure values measured in the two different postures of the spot welding gun 2 and the angle of the wrist unit 15.
For example, as shown in FIG. 4, in the first posture, the moving direction of the movable portion 8 is an angle θ1 in the vertical plane with respect to the vertical downward direction, and the pressing force value is F1. Further, as shown in FIG. 5, in the second posture, the moving direction of the movable portion 8 is an angle θ2 in the vertical plane with respect to the vertically downward direction, and the pressing force value is F2.

角度θ１，θ２は、手首ユニット１５の各軸の角度に基づいて算出することができる。加圧力センサ５により検出される加圧力値Ｆ１，Ｆ２は、駆動部９による加圧力指令値Ｚと可動部８の自重Ｗの移動方向の成分との合力である。
したがって、以下の関係式が成立する。
Ｆ１＝Ｚ＋Ｗｃｏｓθ１
Ｆ２＝Ｚ＋Ｗｃｏｓθ２ The angles θ1 and θ2 can be calculated based on the angles of the respective axes of the wrist unit 15. The pressing pressure values F1 and F2 detected by the pressing force sensor 5 are the resultant force of the pressing force command value Z by the driving unit 9 and the component in the moving direction of the own weight W of the movable unit 8.
Therefore, the following relational expression holds.
F1 = Z + Wcosθ1
F2 = Z + Wcosθ2

上記関係式から、自重算出部１７は、下式の通りに可動部の自重Ｗを算出する。
Ｗ＝（Ｆ１−Ｆ２）／（ｃｏｓθ１−ｃｏｓθ２）
算出された自重Ｗは記憶部１８に記憶される。 From the above relational expression, the self-weight calculation unit 17 calculates the self-weight W of the movable part according to the following formula.
W = (F1-F2) / (cosθ1-cosθ2)
The calculated own weight W is stored in the storage unit 18.

自重Ｗが記憶部１８に記憶された後に、入力部２０の操作により通常運転モードが選択されたときには、モード切替部１９は、制御信号生成部１６を通常運転モードに切り替える。通常運転モードでは、制御信号生成部１６は、ロボット３に対し、予め教示されたプログラムに従う制御信号を生成して出力し、スポット溶接ガン２の駆動部９のサーボモータ１０に対しては、各溶接点におけるスポット溶接ガン２の姿勢と、記憶部１８に記憶されている自重Ｗとに基づいて補正した加圧力指令値Ｚを生成する。 When the normal operation mode is selected by the operation of the input unit 20 after the own weight W is stored in the storage unit 18, the mode switching unit 19 switches the control signal generation unit 16 to the normal operation mode. In the normal operation mode, the control signal generation unit 16 generates and outputs a control signal according to a program taught in advance to the robot 3, and outputs the control signal to the servomotor 10 of the drive unit 9 of the spot welding gun 2. A pressure command value Z corrected based on the posture of the spot welding gun 2 at the welding point and its own weight W stored in the storage unit 18 is generated.

加圧力指令値Ｚは、下式により補正される。
Ｚ＝Ｚ０−Ｗｃｏｓθ
ここで、Ｚ０は所望の加圧力値、θは鉛直平面内における可動部８の移動方向の鉛直下方からの角度である。 The pressurizing command value Z is corrected by the following equation.
Z = Z0-Wcosθ
Here, Z0 is a desired pressing force value, and θ is an angle from vertically below in the moving direction of the movable portion 8 in the vertical plane.

制御信号生成部１６によって生成された制御信号は、ロボット３およびスポット溶接ガン２の駆動部９を構成しているサーボモータ１０にそれぞれ入力される。
通常運転モードにおいては、スポット溶接ガン２に出力する制御信号にはディザ信号は含まれない。 The control signals generated by the control signal generation unit 16 are input to the servomotors 10 constituting the drive unit 9 of the robot 3 and the spot welding gun 2, respectively.
In the normal operation mode, the control signal output to the spot welding gun 2 does not include the dither signal.

このように構成された本実施形態に係るスポット溶接システム１によれば、自重計測モードを選択することにより、ディザ信号が重畳された制御信号がスポット溶接ガン２の駆動部９に供給される。これにより、静止摩擦の影響を低減して、駆動部９が発生している加圧力を精度よく計測することができる。したがって、スポット溶接ガン２の可動部８の自重Ｗを、精度よく計測された加圧力を用いて精度よく算出することができるという利点がある。 According to the spot welding system 1 according to the present embodiment configured in this way, by selecting the self-weight measurement mode, the control signal on which the dither signal is superimposed is supplied to the drive unit 9 of the spot welding gun 2. As a result, the influence of static friction can be reduced, and the pressing force generated by the drive unit 9 can be accurately measured. Therefore, there is an advantage that the own weight W of the movable portion 8 of the spot welding gun 2 can be calculated accurately by using the pressing force measured with high accuracy.

また、本実施形態においては、加圧力指令値Ｚへのディザ信号の重畳を加圧力値の応答の立ち上がり後所定時間経過後に限定している。立ち上がり後所定時間内は駆動部９が停止しておらず静止摩擦が発生していないので、ディザ信号を重畳する必要がない。これにより、ディザ信号を含む制御信号により駆動部９が駆動される時間を短くすることができる。 Further, in the present embodiment, the superimposition of the dither signal on the pressurizing command value Z is limited to a predetermined time after the rise of the response of the pressurizing value. Since the drive unit 9 is not stopped and static friction is not generated within a predetermined time after the rise, there is no need to superimpose the dither signal. As a result, the time for driving the drive unit 9 by the control signal including the dither signal can be shortened.

また、本実施形態においては、加圧力指令値Ｚへのディザ信号の重畳を加圧力値が静定した時点で停止している。加圧力値が静定した後にはディザ信号の有無によって加圧力値の変動はないので、ディザ信号を停止することにより、ディザ信号を含む制御信号により駆動部９が駆動される時間を最小限に短縮することができる。 Further, in the present embodiment, the superimposition of the dither signal on the pressing force command value Z is stopped when the pressing force value has settled down. After the pressure value has settled down, the pressure value does not change depending on the presence or absence of the dither signal. Therefore, by stopping the dither signal, the time for which the drive unit 9 is driven by the control signal including the dither signal is minimized. Can be shortened.

すなわち、本実施形態によれば、ディザ信号の重畳によって静止摩擦の影響を低減しつつ、ディザ信号を重畳する時間を必要最小限に抑えて、ディザ信号を含む制御信号により駆動部９が作動させられることによる影響を未然に防止することができる。ディザ信号を含む制御信号により駆動部９が作動させられることによる影響としては、例えば、フレッチング等の問題を挙げることができる。 That is, according to the present embodiment, the drive unit 9 is operated by the control signal including the dither signal while reducing the influence of static friction by superimposing the dither signal and minimizing the time for superimposing the dither signal. It is possible to prevent the influence of being struck. As an effect of operating the drive unit 9 by a control signal including a dither signal, for example, a problem such as fretting can be mentioned.

そして、本実施形態においては、このようにして静止摩擦の影響を低減して精度よく算出された可動部８の自重Ｗを用いて、各溶接点におけるスポット溶接ガン２の姿勢に応じて、駆動部９に供給する制御信号を補正する。これにより、可動部８の自重Ｗに関わらず、均一な加圧力で、全ての溶接点を加圧しつつスポット溶接を行うことができて、溶接品質を安定させることができるという利点がある。 Then, in the present embodiment, the weight W of the movable portion 8 calculated accurately by reducing the influence of static friction in this way is used to drive the spot welding gun 2 according to the posture of the spot welding gun 2 at each welding point. The control signal supplied to the unit 9 is corrected. As a result, regardless of the weight W of the movable portion 8, spot welding can be performed while pressurizing all the welding points with a uniform pressing force, and there is an advantage that the welding quality can be stabilized.

なお、本実施形態においては、Ｃ型のスポット溶接ガン２を例示したが、これに代えて、Ｘ型のスポット溶接ガン、あるいはスタッド溶接用のスポット溶接ガンに適用してもよい。 In this embodiment, the C-type spot welding gun 2 has been illustrated, but instead, it may be applied to an X-type spot welding gun or a spot welding gun for stud welding.

１ スポット溶接システム
２ スポット溶接ガン
４ 制御装置（制御部）
５ 加圧力センサ
７ 可動溶接チップ（可動電極）
８ 可動部
９ 駆動部
１７ 自重算出部
Ｗ 自重
Ｙ 加圧力値 1 Spot welding system 2 Spot welding gun 4 Control device (control unit)
5 Pressure sensor 7 Movable welding tip (movable electrode)
8 Movable part 9 Drive part 17 Self-weight calculation unit W Self-weight Y Pressure value

Claims (4)

可動電極を含む可動部と、該可動部を駆動する駆動部とを有するスポット溶接ガンと、
前記駆動部を制御する制御部と、
前記スポット溶接ガンの前記可動電極による加圧力を計測する加圧力センサと、
前記可動電極の移動方向を異ならせる前記スポット溶接ガンの異なる２つの姿勢において、前記加圧力センサにより検出された前記加圧力に基づいて前記可動部の自重を算出する自重算出部とを備え、
前記制御部は、前記自重算出部により前記可動部の前記自重を算出する際に用いる前記加圧力の計測に際し、制御信号にディザ信号を重畳して前記駆動部を制御し、前記自重が算出された後には、算出された前記自重に基づいて前記制御信号を補正するスポット溶接システム。 A spot welding gun having a movable portion including a movable electrode and a drive portion for driving the movable portion.
A control unit that controls the drive unit and
A pressure sensor that measures the pressure from the movable electrode of the spot welding gun, and
It is provided with a self-weight calculation unit that calculates the self-weight of the movable portion based on the pressure detected by the pressure sensor in two different postures of the spot welding gun that changes the moving direction of the movable electrode.
The control unit controls the drive unit by superimposing a dither signal on the control signal when measuring the pressing force used when the self-weight calculation unit calculates the self-weight of the movable unit, and the self-weight is calculated. After that, a spot welding system that corrects the control signal based on the calculated own weight. 前記制御部は、前記加圧力センサにより検出される前記加圧力の立ち上がり後所定時間経過後から、前記ディザ信号を前記制御信号に重畳する請求項１に記載のスポット溶接システム。 The spot welding system according to claim 1, wherein the control unit superimposes the dither signal on the control signal after a predetermined time has elapsed after the rise of the pressing force detected by the pressing force sensor. 前記所定時間は、前記ディザ信号を重畳しない制御信号による加圧力値の一定の割合が検出されるまでの時間である請求項２に記載のスポット溶接システム。 The spot welding system according to claim 2, wherein the predetermined time is a time until a constant ratio of a pressing force value by a control signal that does not superimpose the dither signal is detected. 前記制御部は、前記加圧力センサにより検出される前記加圧力が静定した時点で、前記ディザ信号の重畳を停止する請求項１から請求項３のいずれかに記載のスポット溶接システム。
The spot welding system according to any one of claims 1 to 3, wherein the control unit stops superimposition of the dither signal when the pressing force detected by the pressing force sensor has settled down.
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